U.S. patent application number 14/127829 was filed with the patent office on 2014-05-15 for asymmetric perturbation method for a mobile transmit diversity communication device.
This patent application is currently assigned to GOOGLE INC.. The applicant listed for this patent is Sherwin Wang. Invention is credited to Sherwin Wang.
Application Number | 20140135056 14/127829 |
Document ID | / |
Family ID | 46514814 |
Filed Date | 2014-05-15 |
United States Patent
Application |
20140135056 |
Kind Code |
A1 |
Wang; Sherwin |
May 15, 2014 |
ASYMMETRIC PERTURBATION METHOD FOR A MOBILE TRANSMIT DIVERSITY
COMMUNICATION DEVICE
Abstract
A method and apparatus for selectively adjusting transmit
diversity parameters in a mobile communication system including a
mobile device and a base station. The mobile device transmits a
signal set comprised of a plurality of signals differing only in
phase from one another, receive in response an input parameter for
each set, and adjust the phase difference of a subsequently
transmitted signal set as a function of the input parameters.
Inventors: |
Wang; Sherwin; (Towaco,
NJ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Wang; Sherwin |
Towaco |
NJ |
US |
|
|
Assignee: |
GOOGLE INC.
Mountain View
CA
|
Family ID: |
46514814 |
Appl. No.: |
14/127829 |
Filed: |
June 29, 2012 |
PCT Filed: |
June 29, 2012 |
PCT NO: |
PCT/US2012/045018 |
371 Date: |
December 19, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61503932 |
Jul 1, 2011 |
|
|
|
Current U.S.
Class: |
455/522 ;
455/574 |
Current CPC
Class: |
H04B 7/0404 20130101;
H04W 52/0212 20130101; H04B 7/0617 20130101; H04B 7/0671 20130101;
Y02D 70/00 20180101; Y02D 30/70 20200801; H04B 7/0623 20130101;
H04B 7/0682 20130101; Y02D 70/444 20180101 |
Class at
Publication: |
455/522 ;
455/574 |
International
Class: |
H04W 52/02 20060101
H04W052/02 |
Claims
1. A method for delivering an improved wireless transmission signal
set by a mobile device, the method comprising the steps of:
transmitting a plurality of signal sets directed to a base station,
each signal set comprising the same number of signals, all signals
in a set differing only in phase; receiving a plurality of input
parameters, each input parameter corresponding to a transmitted
signal set in response; deriving a received signal quality measure
for said transmitted signal sets as a function of said plurality of
received input parameters; and delivering an improved signal set,
where the delivered phase differences of the signals in the
improved signal set are determined as a function of the received
signal quality measure.
2. The method of claim 1, wherein each input parameter represents a
parameter selected from the group consisting of relative phase,
relative amplitude, absolute power, frequency of modification, and
timing of application of a transmitted signal set.
3. The method of claim 1, where each input parameter is a transmit
power control parameter.
4. The method of claim 1, where each said input parameter
represents a recommendation for improved power levels.
5. The method of claim 1, where the signal quality measure
represents a measure of the received power level.
6. The method of claim 1, wherein said function includes recently
received input parameters.
7. The method of claim 1, wherein said function includes only the
most recently received input parameters.
8. The method of claim 6, wherein said function includes
de-weighting factors applied to input parameters.
9. The method of claim 8, wherein said de-weighting factors weigh
input parameters more heavily based on when each is received.
10. The method of claim 6, where said function accounts for
non-uniform responses by making no adjustment in said improved
signal set as a consequence of input parameters.
11. The method of claim 6, where said function identifies the
majority value among input parameters and accounts for non-uniform
values by making adjustment in said improved signal set based on
the majority.
12. The method of claim 11 where the extent of the adjustment is
proportional to the extent of the majority.
13. The method of claim 6, wherein the number of input parameters
included in said function is an even number, and if there is no
majority value of input parameters, said function makes no
adjustment in said improved signal set based on said input
parameters.
14. The method of claim 1, where each signal in a signal set is
transmitted by a different antenna.
15. A mobile subscriber unit apparatus adapted to deliver an
improved wireless transmission signal set comprising: a transmitter
to transmit signal sets directed to a base station, a receiver to
receive an input parameter in response to a transmitted signal set,
a processor to derive a calculated received signal quality measure,
and a signal generator to generate a plurality of signals for
transmission; wherein said transmitter transmits a plurality of
signal sets directed to a base station, in response said receiver
receives one input parameter per transmitted signal set, said
processor calculates a received signal quality measure as a
function of a plurality of received input parameters, and said
signal generator generates an improved signal set for transmission
to said base station, and wherein each signal set comprising the
same number of signals and all signals in a set differing only in
phase; and wherein the delivered phase differences of the signals
in the improved signal set are determined as a function of the
received signal quality measure.
16. The apparatus of claim 15, wherein said input parameter
represents a parameter selected from the group consisting of
relative phase, relative amplitude, relative power, absolute power,
frequency of modification, and timing of application of a
transmitted signal set.
17. The apparatus of claim 15, where the input parameter is a
transmit power control parameter.
18. The apparatus of claim 15, where each said input parameter
represents a recommendation for improved power levels.
19. The apparatus of claim 15, where the signal quality measure
represents a measure of the received power level.
20. The apparatus of claim 15, wherein said function includes
recently received input parameters.
21. The apparatus of claim 15, wherein said function includes only
the most recently received input parameters.
22. The apparatus of claim 20, wherein said function includes
de-weighting factors applied to input parameters.
23. The apparatus of claim 22, wherein said de-weighting factors
weigh input parameters more heavily based on when each is
received.
24. The apparatus of claim 20, where said function accounts for
non-uniform responses by making no adjustment in said improved
signal set as a consequence of input parameters.
25. The apparatus of claim 20, where said function identifies the
majority value among input parameters and accounts for non-uniform
values by making adjustment in said improved signal set based on
the majority.
26. The apparatus of claim 25 where the extent of the adjustment is
proportional to the extent of the majority.
27. The apparatus of claim 20, wherein the number of input
parameters included in said function is an even number, and if
there is no majority value of input parameters, said function makes
no adjustment in said improved signal set based on said input
parameters.
28. The apparatus of claim 15, where each signal in a signal set is
transmitted by a different antenna.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit of U.S. Provisional Patent
Application Ser. No. 61/503,932, entitled "ASYMMETRIC PERTURBATION
METHOD FOR A MOBILE TRANSMIT DIVERSITY COMMUNICATION DEVICE" filed
Jul. 1, 2011, the entirety of which is incorporated by reference
herein.
FIELD
[0002] This disclosure relates generally to the field of mobile
wireless communications and more specifically to adjusting phase in
a mobile transmit diversity communications device using asymmetric
perturbation, wherein the phase is adjusted as a means to control
the power level received at a base station.
BACKGROUND
[0003] A transmit diversity communication device is one having a
plurality of transmit paths that simultaneously transmit respective
transmit signals that differ by a transmit diversity signal, for
example, a relative phase, relative amplitude, or relative power.
One goal of mobile transmit diversity is to obtain constructive
interference, also known as beamforming, of the transmit signals at
the receiver, e.g., a base station.
[0004] In transmit diversity systems, one possible advantageous
feature is an extension of operating range. This effect may be an
outcome of forming a beam using the plurality of transmit paths
that exhibits a higher Effective Radiated Power (ERP) at the base
station than a conventional (non-diversity) transmitter
transmitting using a single transmit path. Transmit beamforming can
be performed by using feedback information from the receiver to the
transmit diversity transmitter in adjusting the value of the
transmit diversity parameter.
[0005] As described in prior patent applications of the assignee of
the present disclosure, a mobile transmit diversity (MTD) device
may use two antennas simultaneously transmitting with a transmit
diversity parameter, for example, a phase difference or a power
ratio between at least two antennas. In one implementation, two
power amplifiers may be used to amplify the respective transmit
signals, thereby potentially providing a current (i.e., power)
saving by the mobile device. Use of mobile transmit diversity may
permit extending the effective range of a mobile device from a base
station using the same (or less) power as a non-diversity
transmission device.
[0006] When configured to provide beam forming MTD, the relative
phase between the two paths may be adjusted such that the signals
arrive at the base station antenna in-phase to constructively add.
In this case the performance is higher than achieved with just the
sum of the two powers combined. The difference is diversity gain
(Gd).
[0007] Because a mobile transmit diversity device may obtain a
diversity gain at the receiver using feedback to provide
beamforming, current consumption efficiency gains may be produced.
For example, a suitable receive power may be obtained by operating
one or more of the amplifiers at less than half the specification
power of the device. Accordingly, one or both of the amplifiers may
be operated to provide maximum efficiency at a fraction, e.g., half
or even a quarter of the specification power of the device.
SUMMARY OF THE PRESENT DISCLOSURE
[0008] The present implementations are directed to a transmit
diversity approach, whereby the mobile device receives an input
parameter from a base station in response to a transmitted
plurality of signals, and the mobile devices uses a series of such
input parameters to adjust a transmit delivery parameter.
[0009] In the following description, the transmit diversity
parameter used for purposes of illustration is phase difference
between two transmit paths. It will be understood that more than
two transmit paths may be used within the scope of the disclosure.
Likewise, different or additional transmit diversity parameters,
e.g., power ratio, may be used. It will also be understood that
transmit power control (TPC) signals are used as an illustration of
a signal quality indicator, but that alternatively or additionally,
other signal quality indicators may be used.
[0010] According to implementations of the disclosure, the mobile
device may transmit data with a plurality of different phase
differences, for example, progressively changing in a positive or
negative direction from a reference phase, and make further
decisions according to the respective plurality of TPC feedback
signals received in response to the signals. For example, an
initial phase difference may be .phi..sub.0. The mobile device may
then transmit at least the next two transmit signals with phase
difference changing in a single direction, e.g., phase differences
.phi..sub.1 and .phi..sub.2, where
.phi..sub.0<.phi..sub.1<.phi..sub.2 or
.phi..sub.0>.phi..sub.1>.phi..sub.2. In response, the base
station will transmit a commensurate number of TPC feedback
signals, e.g., one for each of .phi..sub.1 and .phi..sub.2. It will
be understood that in the present illustration, two phase
differences are provided, but more than two phase differences,
e.g., three, four, or five, phase differences may be used in
sequence, and a commensurate number of feedback signals
gathered.
[0011] According to implementations of the disclosure, when
transmitting a signal, the device may transmit the same signal
using phase differences. That is a signal may be transmitted as a
signal set, with the signals in the signal set containing the same
content, but differing in phase.
[0012] The receiver at the base station has the ability to
recognize the received power, which may be consequential to a
combination of signals, differing only in phase. This combination
of signals may serve the function of beam forming. In response, the
base station may return a parameter which can be interpreted by the
device as indicating whether the received power level was too high
or too low. For example, the returned parameter can be a single
bit, where 1 indicates that the power level was higher than
necessary and 0 indicates that the power level was lower than
necessary.
[0013] The device can then store the parameters returned and can
use the stored information to determine an adjustment in phase.
[0014] In the present implementation, the device can adjust phase
based on the parameters in a number of ways. For example, the
device can adjust phase based on the most recent returned
parameter, the most recent returned quantity of parameters (such as
2, 3, 4, or 5), alternate received parameters, or weighting factors
applied to the most recent parameters.
[0015] The above is a brief summary of a number of unique aspects,
features, and advantages of the present disclosure. The above
summary is provided to introduce the context and certain concepts
relevant to the full description that follows. However, this
summary is not exhaustive. The above summary is not intended to be
nor should it be read as an exclusive identification of aspects,
features, or advantages of the claimed subject matter. Therefore,
the above summary should not be read as imparting limitations to
the claims nor in any other way determining the scope of said
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The subject matter regarded as the disclosure is
particularly pointed out and distinctly claimed in the concluding
portion of the specification. The disclosure, however, both as to
organization and method of operation, together with objects,
features, and advantages thereof, may best be understood by
reference to the following detailed description when read with the
accompanying drawings in which:
[0017] FIG. 1 is a schematic diagram of a system according to an
implementation of the disclosure;
[0018] FIG. 2 is a schematic diagram of amplifier efficiency versus
a range of output power of a full power and half power PAs in
accordance with an implementation of the disclosure;
[0019] FIGS. 3A and 3B are schematic diagrams of devices according
to implementations of the disclosure;
[0020] FIG. 4 depicts a chart of an example of delivered phase over
time for a two-signal symmetric phase perturbation system, where
the signal is delivered from a UE to a base station.
[0021] FIG. 5 depicts a chart of an example of delivered phase over
time for a two-signal asymmetric phase perturbation system, where
the signal is delivered from a UE to a base station.
[0022] FIG. 6 depicts a chart of an example of delivered phase over
time for a three-signal asymmetric phase perturbation system, where
the signal is delivered from a UE to a base station.
[0023] FIG. 7 is a schematic flow chart diagram of a method in
accordance with implementations of the present disclosure; and
[0024] FIG. 8 is a schematic flow chart diagram of a method in
accordance with an implementation of the present disclosure.
DETAILED DESCRIPTION
[0025] Implementations of the disclosure may be used in
communication systems in connection with mobile transmit diversity
devices. A communication system may include a mobile transmitter,
also referred to as a modifying communication device, that adjusts
a nominal value of a transmit diversity parameter, for example, a
phase difference and/or a power ratio between a signal transmitted
on a first antenna and a second antenna. Although the
implementations described in the present application are described
as using two antennas, it will be recognized that the present
disclosure is equally applicable to transmit diversity systems and
devices having more than two antennas.
[0026] In the following detailed description, numerous specific
details are set forth in order to provide a thorough understanding
of the disclosure. However, it will be understood by those skilled
in the art that the present disclosure may be practiced without
these specific details. In other instances, well-known methods,
procedures, and components have not been described in detail so as
not to obscure the present disclosure.
[0027] Although implementations of the disclosure are not limited
in this regard, the terms "plurality" and "a plurality" as used
herein may include, for example, "multiple" or "two or more". The
terms "plurality" or "a plurality" may be used throughout the
specification to describe two or more components, devices,
elements, units, parameters, or the like. Unless explicitly stated,
the method implementations described herein are not constrained to
a particular order or sequence. Additionally, some of the described
method implementations or elements thereof can occur or be
performed simultaneously, at the same point in time, or
concurrently.
[0028] The present disclosure may be applicable in any
communication network between a mobile device and a second
communication device, including but not limited to a base station.
Networks may utilize communication protocols and technologies to
provide the communication sessions. Examples of communication
protocols and technologies include those set by the Institute of
Electrical and Electronics Engineers, Inc. (IEEE) 802.xx standards,
International Telecommunications Union (ITU-T) standards, European
Telecommunications Standards Institute (ETSI) standards, Internet
Engineering Task Force (IETF) standards, or other standards.
[0029] Communication devices in a network may use any suitable
multiple access technology, for example, a code division multiple
access (CDMA) technology. According to one implementation, the
network may operate according to a CDMA 2000 telecommunications
technology that uses a single CDMA channel. As an example, a
CDMA2000 high rate data packet technology, such as the Evolution
Data Optimized (EVDO) technology may be used.
[0030] The network may comprise any suitable communication network.
A communication network may comprise all or a portion of a public
switched telephone network (PSTN), a public or private data
network, a local area network (LAN), a metropolitan area network
(MAN), a wide area network (WAN), a global computer network such as
the Internet, a wireless network, a local, regional, or global
communication network, an enterprise intranet, other suitable
communication link, or any combination of the preceding.
[0031] A component of a network, for example, a mobile
communication device, may include logic, an interface, memory,
other component, or any suitable combination of the preceding.
"Logic" may refer to hardware, software, other logic, or any
suitable combination of the preceding. Certain logic may manage the
operation of a device, and may comprise, for example, a processor.
"Interface" may refer to logic of a device operable to receive
input for the device, send output from the device, perform suitable
processing of the input or output or both, or any combination of
the preceding, and may comprise one or more ports, conversion
software, or both. "Memory" may refer to logic operable to store
and facilitate retrieval of information, and may comprise a Random
Access Memory (RAM), a Read Only Memory (ROM), a magnetic drive, a
disk drive, a Compact Disk (CD) drive, a Digital Video Disk (DVD)
drive, a removable media storage, any other suitable data storage
medium, or a combination of any of the preceding.
[0032] The communication network may include one or more mobile or
modifying communication devices and one or more other communication
devices, for example base stations that communicate via a wireless
link. A mobile communication device unit may comprise any device
operable to communicate with a base station, for example, a
personal digital assistant (PDA), a cellular telephone, a mobile
handset, a laptop computer, or any other device suitable for
communicating signals to and from a base station. A subscriber unit
may support, for example, Session Initiation Protocol (SIP),
Internet Protocol (IP), or any other suitable communication
protocol.
[0033] A base station may provide a subscriber unit access to a
communication network that allows the subscriber unit to
communicate with other networks or devices. A base station
typically includes a base transceiver station and a base station
controller. The base transceiver station communicates signals to
and from one or more subscriber units. The base station controller
manages the operation of the base transceiver station.
[0034] According to implementations of the disclosure, the mobile
communication device may include two or more antenna elements,
where each antenna element is operable to receive, transmit, or
both receive and transmit a signal. Multiple antenna elements may
provide for a separation process known as spatial filtering, which
may enhance spectral efficiency, allowing for more users to be
served simultaneously over a given frequency band.
[0035] As described more fully below, according to implementations
of the present disclosure, the mobile communication device may
include a processor and a transmit/receive module that calculate
and produce one or more signals for transmission over a plurality
of antennas.
[0036] According to one implementation, modifying a signal may
refer to modifying a signal feature. For example, a signal may be
transmitted by the two antennas using a modified signal feature, or
a different value of a transmit diversity parameter. A transmission
signal feature, or in some implementations of the disclosure, a
transmit diversity parameter, may refer without limitation to any
feature of the transmission, for example, relative phase, relative
amplitude, relative power, absolute power, frequency, timing, other
suitable signal feature that may be modulated, or any combination
of the preceding. Relative phase may refer to the phase difference
between signals in the same signal set, such as the phase of a
signal transmitted by a first transmit antenna and the phase of a
signal transmitted by a second transmit antenna. Relative power may
refer to the ratio between the power of a first signal of a first
transmit antenna element and the power of a second signal of a
second transmit antenna element, which ratio may be defined on a
linear or logarithmic scale. Relative amplitude may refer to the
ratio between the amplitude of a first signal of a first transmit
antenna element and the amplitude of a second signal of a second
transmit antenna element. Absolute power may refer to the total
power transmitted by all antennas of modifying communication
device. According to one implementation, modifying a signal may be
described as adjusting a nominal value of a transmit diversity
parameter.
[0037] According to implementations of the disclosure, a diversity
parameter may be a parameter distinguishing between the
transmission on any two antennas, for example a difference in
transmission phase on the two antennas, or a ratio of transmission
power on the two antennas. It will be understood that although
examples are provided in the present application pertaining to
phase difference between two antennas, the disclosure is applicable
using the same principles to varying any transmit diversity
parameter.
[0038] Mobile user equipment devices (UEs) using beam forming
transmit diversity (MTD) may typically use two transmit chains each
including, but not limited to a phase modulator (PM), power
amplifier (PA) and primary and secondary antennas.
[0039] In a typical operation, the base station may adjust the
transmitted power of the UE with a TPC feedback command so as to
limit the transmitted power to be no higher than necessary, or so
as to increase the transmitted power to overcome fading.
[0040] Using TPC to Adjust Relative Phase
[0041] The transmit diversity parameter may be modified in order to
provide beamforming at the base station. In one implementation of
MTD, the UE may employ an algorithm using the TPC to adjust the
relative phase between the transmitted signals and observe the
effect on the power command received by the UE. The power command
may be a "power up" or "power down" command, which respectively
suggest the appropriateness of increasing or decreasing power
levels. The phase adjusting algorithm may assume the phase setting
that produces a "power down" command is at a more nearly optimum
constructive phase than a phase setting that produces a "power up"
command. This cause and effect process is constantly adjusting the
relative phase to maintain the signals' relationship in spite of
changing geometry of the UE with respect to the base station and
through varying propagation conditions. In another implementation
of MTD, the base station may expressly instruct the UE how to
modify the phase difference so as to improve reception.
[0042] It will be understood that implementations of the disclosure
may be used in connection with any type of transmit diversity
feedback, including without limitation, "open-loop" feedback, which
uses a feedback parameter not dedicated to transmit diversity such
as a TPC signal for adjusting the transmit diversity parameter, or
"closed-loop" feedback, which determines the present value of a
transmit diversity parameter or its component parts, and uses a
dedicated transmit diversity feedback, e.g., an explicit
instruction from the base station to adjust the transmit diversity
parameter.
[0043] When a mobile device accesses the wireless network at the
cell edge, especially when uploading data at peak possible rate it
is transmitting at high power; MTD may provide a battery power
savings by virtue that diversity gain allows the use of lower
transmitter power to provide the same Effective Isotropically
Radiated Power (EIRP) than a non-diversity unit. Therefore, at cell
edge, where the propagation losses are high, or in high fading
situations, the diversity gain may provide continued operation,
even when a non-diversity UE would cease to maintain a connection
as well as higher data rate and better quality than a single
antenna UE. However, when only low transmitter powers are required,
for example, e.g. when the UE is close to the base station or when
in mid range but at low data rate, reduced power amplifier
efficiency at low power plus the additional operating current of
the Phase Modulator (PM) or the additional RF channel required to
route the baseband resident PM, may result in a decreased battery
life than would be provided by a non-diversity UE in a similar
situation. Implementations of the disclosure may allow MTD devices
to employ power saving when doing so would be beneficial, but not
to suffer excessive power consumption when doing so would be
costly. According to some implementations of the disclosure, some
excessive power consumption, within a predetermined limit, may be
acceptable for a possible gain in network capacity.
[0044] FIG. 1 is a schematic diagram of a system according to an
implementation of the disclosure. FIG. 1 depicts a mobile
communication device (UE) having a plurality of antennas in
wireless communication with a base station. Although two antennas
are shown, it will be understood that principles of the disclosure
are equally applicable to a UE with more than two antennas, which
is also within the scope of the present disclosure.
[0045] In some implementations of the disclosure, the mobile device
may include two or more transmit paths, or channels, each
associated with a respective transmit antenna. Such a transmit path
may include, for example, an RF power amplifier' and a transmit
antenna. One or more of the transmit paths may include a diversity
parameter adjustment module, e.g., a phase modulator if the
transmit diversity parameter is a relative phase.
[0046] Also shown in FIG. 1 is an example of mobile transmit
diversity on the uplink with beam forming. In the example shown,
signals .phi..sub.1 and .phi..sub.2 are being transmitted. The
example assumes a reference phase .phi..sub.0, with .phi..sub.1 and
.phi..sub.2 each being offset from .phi..sub.0. In the example,
both signals are transmitted toward the base station.
[0047] According to implementations of the disclosure, current loss
may be avoided in low power conditions, when non-diversity
operation is enabled (or diversity operation disabled). Disabling
MTD may involve powering down, e.g., disconnecting from a power
source or switching to standby mode, the phase modulator and/or
half-power amplifier, or disabling the second RF path that routes
the baseband residing phase modulator. Current savings may refer to
a decrease in the power drawn by the UE in total, particularly in
relation to a real or hypothetical non-diversity transmitter
operating in similar conditions.
[0048] FIG. 2 is a schematic diagram of a device according to an
implementation of the disclosure. As shown, the mobile
communication device may include a transceiver (410) and at least
two transmit paths. A primary transmit path (430) may be associated
with a primary power amplifier (460), which may provide signal
amplification to the full specification power of the device, and a
secondary transmit path (470) associated with a secondary power
amplifier (440), which may provide signal amplification to a
fraction, e.g., half, of the specification power of the device.
Each path may have a respective associated antenna. The device may
include one or more diversity parameter modulators, e.g., a phase
modulator (420), which may be associated with one or more transmit
paths. It will be recognized that the phase modulator may comprise
a plurality of phase modulators on each or both of the transmit
paths. A controller (450) may be connected to receive inputs and
produce outputs to control various operations of the transmit
paths, as described herein. For example, the controller may provide
an enabling/disabling signal to any or all of the phase modulator
(420), the primary power amplifier (460), and the secondary power
amplifier (440).
[0049] It will be recognized that although the implementation of
FIG. 2 shows full- and half-power amplifiers, in other
implementations of the disclosure, the amplifiers may both be
fractional power, having different fractions of specification
power,eg, half and quarter power, or similar fractional powers,
e.g., both half of specification power, or may both be full-power
amplifiers. For example, in some implementations of the disclosure,
the power amplifiers on the respective transmit paths may have the
same transmit power, e.g., each may be rated for a fraction (e.g.,
half or quarter) of the specification power limit of the device as
a whole based on its class. It will be further understood that the
optimal efficiency of an amplifier may be modified by altering its
supply voltage. Thus, for example, a "full-power" power amplifier
may be turned into a "half-power" power amplifier by halving its
supply voltage, thereby shifting its point of optimal efficiency to
half the power.
[0050] According to implementations of the disclosure, as described
below, the mobile communication device may use both power
amplifiers in transmit diversity as described above, and then,
e.g., in response to a condition as described below, use only one
of the power amplifiers, e.g., the primary amplifier, in
non-diversity transmit mode. In such implementations, although
diversity gain may be given up by transmitting over one transmit
path or the other, one antenna may be a better choice due to power
consumption considerations.
[0051] Although additional implementations of the disclosure
described below refer to two amplifiers, e.g., a high power
amplifier and a low power amplifier, or a full-power and half-power
amplifier, it will be understood that the methods described are
fully applicable to implementations having more than two power
amplifiers.
[0052] In some implementations of the disclosure, the power
amplifiers in the transmit paths may be rated for a different
output power. For example, a first power amplifier in a first
transmit path may be rated to transmit a high power and a second
power amplifier in a second transmit path may be rated to produce a
lower power. More specifically, as depicted an implementation of
the disclosure shown in FIG. 2, the first power amplifier may be
rated to transmit a full power allocated to the device unit of its
class, e.g., +24 dBm, and be connected to the primary antenna, and
the second power amplifier may be rated to transmit a fraction,eg,
half, of the full power allocated to the device unit of its class,
e.g., +21 dBm, and be connected to the secondary antenna.
[0053] It will be recognized that when employing transmit
diversity, the base station may receive a signal power level
approximately equal to effective received power Pe, where
Pe=[Pt+Antennas gain+Gd-Power Loss in Path]. Pt may be the-power
Pout driving the mobile's antennas assembly, and Gd is the
diversity gain provided by coherently transmitting more than one
signal. If the mobile device is transmitting at the maximum power
allowed by its class, the range from the base station with which it
can operate satisfactorily may be extended past a non-diversity
mobile device because of the diversity gain Gd. Less power may be
used for transmission by a diversity mobile device than a
non-diversity mobile device in order to maintain the same range,
which may lead to a potential current consumption saving.
[0054] According to some implementations of the disclosure, the UE
includes a transceiver as shown in FIG. 2, and may include
providing the drive signal to a Phase Modulator (420). The Phase
Modulator (420) may apply to the transmitted signals a phase shift
between the primary and secondary transmit paths.
[0055] According to an implementation of the disclosure, the
primary transmit path (430) may include a full-power power
amplifier (PA) (460) and the secondary transmit path (470) may
include a half-power PA (440).
[0056] According to some implementations of the disclosure, the UE
transmitter may be switched between diversity and non-diversity
operation. The switching action may at least in part be based on a
condition associated with the level of transmitted power.
Transmitted power may refer to any or all of the transmit power of
one or both of the transmit paths, the power received by a station,
or a substitute parameter such as received power, or the like.
[0057] In order to selectively activate or deactivate diversity
transmission, the diversity controller may place the Phase
Modulator and/or Full Power PA in active or standby mode, or shut
it off, for example, by changing the value of an
enable/disable/standby input pin, depending on whether diversity
operation (active) or non-diversity operation (standby) are
commanded. As described below, switching may be affected by
additional parameters, e.g., capacity considerations such as
refraining from switching during increased transmission activity,
and/or mobility detection, e.g., anticipating a trend in transmit
power based on motion of the UE towards or away from a base
station.
[0058] FIG. 3A is a schematic diagram of a device according to an
implementation of the disclosure (500). As shown, the mobile
communication device may include a baseband processor (505) and at
least two transmit paths. Each of the transmit paths may include an
RF transmit up converter, an RF receive down converter, an
amplifier, a duplex module, and an antenna. A down converter may
refer to a module that converts an input signal centered at a radio
frequency, for example, as received by the antenna, or an
intermediate frequency to a baseband signal centered at the zero
frequency. An up converter may refer to a module that converts an
input baseband signal centered at the zero or Intermediate
frequency to an RF signal centered around the transmission
frequency for transmission by the antenna. Accordingly, for
example, a primary receive path may be associated on the receive
side with a receive RF down converter (515), and on the transmit
side with a transmit RF up converter (510), which may be shared
with the secondary transmit path, and a high or full power
amplifier (550), which may provide signal amplification to the full
specification power of the device. The primary transmit and receive
paths may share an antenna (535) using a duplex module (530).
Likewise, a secondary transmit path may be associated on the
transmit side with the shared transmit RF up converter (510) and a
low or fractional power amplifier (555), which may provide signal
amplification to a fraction of the full specification power of the
device, and on the receive side with an RF receive down converter
(520). The secondary transmit and receive paths may share an
antenna (540) using a duplex module (545). The device may include
one or more diversity parameter modulators, e.g., a phase modulator
(525), which may be associated with one or more transmit paths. In
the implementation shown, the phase modulator (525) may be a
separate module that receives an up converted signal from the
baseband processor and produces two transmit signals differing by a
diversity parameter.
[0059] FIG. 3B depicts an alternative implementation of the
disclosure (501), in which the phase modulation is not performed by
a separate module, but rather, is performed directly by the
baseband processor in the baseband frequency prior to up conversion
to the RF frequency. In the implementation shown, each of the
primary and secondary transmit paths may have its own RF up
converter module (560 and 565). It will be recognized that the
principles of the disclosure apply to the implementations depicted
in FIGS. 3A and 3B, as well as other configurations.
[0060] The baseband processor (505) may be connected to receive
inputs and produce outputs to control various operations of the
transmit paths, as described herein. For example, the controller
may provide enabling/disabling signals to any or all of the phase
modulator, the primary and secondary power amplifiers, and the RF
transmit up converters. In the implementation depicted in FIG. 3A,
the baseband processor (505) may be connected and able to
disconnect or place on standby the phase modulator (525), and the
secondary power amplifier (555). In the implementation depicted in
FIG. 3B, the baseband processor (505) may be connected and able to
disconnect or place on standby the secondary RF up converter module
(565), and the secondary power amplifier (555).
[0061] According to an implementation of the disclosure, an offline
measurement and calibration procedure may be performed to set
threshold values that may be used in online operation of the mobile
device. Offline may refer to a UE state during production or when
the UE is not actively transmitting a data signal to a base
station, such as during a power up cycle.
[0062] In one such calibration, using mobile transmit diversity,
the mobile device may first perform an offline measurement of
diversity operation, for example, mapping a plurality of possible
Pout levels against the digital calibration table in the baseband
processor. Accordingly, for each such possible Pout level, the
current consumption of the entire transmission circuitry (e.g., the
two RF up converters, the phase modulator (s), the power
amplifiers, and any other active circuitry related to the transmit
chain used in the UE) may be measured. Next, with the mobile
transmit diversity off (non-diversity operation), the UE may
disconnect the diversity transmission components (e.g., the phase
modulator, the secondary power amplifier, and the secondary RF up
converter) from the power supply, and repeat the measurement of
current consumption for various power levels. It will be recognized
that the various components involved in diversity or non-diversity
transmission may vary from implementation to implementation. For
example, in the implementation depicted in FIG. 3B, there may not
be a phase modulator whose current consumption is to be measured.
Furthermore, it will be recognized that the UE may place various
diversity transmission modules or components in standby mode,
rather than necessarily disconnecting them from power.
[0063] According to some implementations of the disclosure, in
operation, the UE may be switched between diversity and
non-diversity operation. The switching action may at least in part
be based on a condition associated with the level of transmitted
power. Accordingly, after offline calibration, the UE may have
stored a correlation between power (or current) consumption in
diversity or non-diversity operation for each of a variety of
transmission power levels. Such a look up table may be used during
online operation in order to compare a power (or current)
consumption in an operative transmission mode (e.g., diversity) to
a threshold based on the stored power consumption in the
alternative transmission mode (e.g., non-diversity). It will be
recognized that while current consumption is discussed herein as a
measure of power, other parameters may be used for measurement
and/or comparison. For example, if a voltage may be varied, for
example, when using lower voltage to supply power to an amplifier
in a fractional power mode, the voltage may likewise be taken into
consideration. In some implementations, other parameters, e.g., a
TPC signal or sequence, receive power, and/or signal quality
indicators, may be used in the power consumption calculations.
[0064] According to an implementation of the disclosure, the
offline calibration may be performed by using the UE enabled to MTD
operation and measuring various power parameters. Measurements may
include power and/or current draw and other characteristics of the
components or whole transmit paths of the UE. The measurements may
be used to map possible levels of the transmit power versus a
calibration table. The calibration table may refer to a data
reference referred to below used to calculate the threshold level
or may refer to a separate data reference. Possible transmit power
values may refer to all or a plurality of possible power levels,
all or a plurality of possible power levels in the operational
range of the UE, or a sample of all or a plurality of possible
power levels, which may be sampled at defined increments.
[0065] According to one implementation of the disclosure, for each
possible transmit power level, the current consumption of the
entire transmission circuitry may be measured and recorded or
stored in a memory. The entire transmission circuitry may include a
phase modulator (if separate), two power amplifiers, and/or other
active circuitry of the UE, e.g., one or more transmit RF up
converters.
[0066] The calibration process may then use an MTD enabled UE
operating with the MTD off. The power supply or plurality of
supplies may be disconnected from the transmit diversity circuitry
or modules, e.g., a phase modulator (if any), the secondary power
amplifier, and/or a transmit RF up converter. According to an
implementation of the disclosure, the transmit diversity components
may be disconnected from the power supply. According to some
implementations of the disclosure, power disconnection may refer to
a standby mode.
[0067] According to some implementations of the disclosure, the
calibration process may generate a table or other form of data
reference for all possible transmit power levels, which may be
stored in a memory of the UE for use during online operation. Such
a table may contain a plurality of entries representing current
consumption differences between MTD on operation and MTD off
operation. According to one implementation of the disclosure, the
table may include additional parameters for consideration during
online comparisons, e.g., current consumption differences
corresponding to a plurality of transmit diversity gains (Gd),
e.g., 1 dB, 2 dB, or 3 dB.
[0068] According to one implementation of the disclosure, a further
method may be used calculate a current consumption difference for a
given pair of power and Gd values. For each db of gain Gd the
maximum possible transmit power of the table may be a defined
number of dB lower corresponding to the value of the Gd in dB. This
may cause the current drawn to be lower per the same calibration
table. The table representing the current consumption difference
containing values representing MTD on operation and MTD off
operation may be created by shifting both values for each transmit
power level a number of transmit power levels corresponding to the
value of Gd in dB, such that the current saving may be increased
for every transmit power. For example, if the Gd is 2 dB, the
values corresponding to diversity and non-diversity operation in
the table may be shifted by 2 places, such that the current saving
gain for each transmit power may increase and respectively the
current losses at low level transmit power may be reduced.
[0069] In order to selectively activate or deactivate diversity
transmission, the diversity controller may place the Phase
Modulator, Full Power PA and/or the associated TX up converter in
active or standby mode, for example, by changing the value of an
enable/disable input pin, depending on whether diversity operation
(active) or non-diversity operation (standby) is warranted. As
described below, switching may be affected by additional
parameters, e.g., capacity considerations such as refraining from
switching during increased transmission activity, and mobility
detection, e.g., anticipating a trend in transmit power based on
motion of the UE towards or away from a base station.
[0070] In transit diversity using asymmetric perturbations, a
signal is sent more than once, where the content of the signals is
the same, but they are transmitted out of phase from one another.
This method of transmission can be used for beamforming. In the
present disclosure, the receiver, typically a base station, can use
the phase difference to determine if the received power was too
high or too low. The base station can return an indicator of
whether the received power was too high or too low, and the
transmitter can use that information to adjust a subsequent signal
set. To account for the power level being too high or too low, the
transmitter can adjust the phase differentials in the subsequent
set of transmitted signals.
[0071] FIGS. 4-6 show examples of phase perturbation techniques
which may be employed. FIG. 4 shows symmetric phase perturbations
with regard to transmit diversity in a mobile communication system.
The example of FIG. 4 shows a two-signal application. In symmetric
phase perturbations, signals are uniformly offset from a reference
phase .phi..sub.0. Phases .phi..sub.1 and .phi..sub.2 are equally
offset from reference phase .phi..sub.0, where, in the Example of
FIG. 4, .phi..sub.1 is offset in a positive direction and 92 is
offset in a negative direction.
[0072] FIG. 5 depicts an example of a two-signal asymmetric phase
perturbation. In this example, phases .phi..sub.1 and .phi..sub.2
are transmitted, but are offset differently from one another
relative to reference phase .phi..sub.0. In the example shown,
.phi..sub.1-.phi..sub.0 is greater than .phi..sub.2-.phi..sub.0.
Although both differences are shown as positive, the differences
may not necessarily be of the same sign.
[0073] FIG. 6 depicts an example of a three-signal asymmetric phase
perturbation. In which phases .phi..sub.1, .phi..sub.2, and
.phi..sub.3 are transmitted and, as shown by example,
.phi..sub.2=.phi..sub.0, although .phi..sub.2 need not equal
.phi..sub.0, and the transmitted phases need not be uniformly
distributed (as shown in the figure).
[0074] In the present disclosure, in response to the UE
transmitting a signal set where the signals differ only in phase,
the base station responds with a parameter, which preferably is
indicative of the received power. This parameter is generally
referred to herein as a TPC, where a TPC is sent from the base
station in response to each group of signals. Preferably, the TPC
is a single bit, although more bits may also be included in a TPC
string.
[0075] FIG. 7 shows a flow chart of a method of the present
disclosure. The UE transmits a plurality of signals along different
paths (610). Preferably the UE sends two signals using two
antennae, but more may also be sent and the signals may be sent
using any number of antennae. The signals are directed to a base
station and, following receipt of the signals, for each signal
received, the base station returns a signal indicating signal
quality of the received signal (620). This signal quality indicator
provides adequate information for the UE to understand whether the
earlier signals might be adjusted in some way so as to improve
efficiency or performance. Based on the indicators received, the UE
determines if the most recently transmitted signals are at too high
or too low a power level (630). The UE then determines if these
recently transmitted signals are the only signals in which it
received feedback indicators (640). If they are the only signals,
an algorithm adjusting one or more transmit parameters, where the
algorithm is based on the feedback indicators and previous transmit
parameters is applied (660), If there are other signals relative to
which feedback indicators had been received, the algorithm is
changed to introduce aspects of those transmit signals and feedback
indicators (650). The revised algorithm is then applied (660). The
transmit parameters resulting from the algorithm are then used to
transmit a new set of signals along different paths (610) and the
process is repeated.
[0076] FIG. 8 shows a flow chart of a variation of the method shown
in FIG. 7. The UE transmits a plurality of signals along different
paths (710). Feedback results are then obtained (720). Then the UE
performs a combination of steps to adjust the phases of the next
transmissions (730), where the UE may perform any or all of the
steps of analyzing results for strong and weak recommendations
(740), determining recent feedback indicators, adjustments, and
results (750), and applying one or more de-weighting factors (760).
The result is to enter results into an algorithm (770) and then
repeating the process by transmitting a plurality of signals along
different paths (710). The strong and weak indicators may be based
on a combination of recent input parameters. For example, the
majority of parameters may be used to adjust phase differences in a
particular way, the strength of the majority may be used to further
adjust the phase differences, the weakness of a majority may result
in limited changes, or the lack of a majority may result in other
changes. Certainly, other types of analysis may be performed on the
input parameters so as to result in changes in phase. As another
example, a pre-selected quantity of input parameters may be used,
only selected input parameters may be used, or recent results may
be used as further input to phase changes. In summary, an algorithm
may be implemented as a function so as to determine changes to
phase differences.
[0077] Mobile transmit diversity (MTD), also known as uplink
transmit diversity (ULTD), allows mobile devices in a cellular
telecommunications system to save transmit power, extend cell
range, and attain other benefits, by transmitting a diversity
signal on two or more antennas simultaneously. The signals differ
by a diversity parameter, typically, a phase difference. Feedback
from the base station in communication with the mobile device
allows the mobile device to adjust a diversity parameter, thereby
allowing beamforming by the mobile device to increase perceived
receive power of the combined signal at the base station. The
feedback may be any signal from the base station, for example, a
quality indication signal, e.g., transmit power control signal
instructing the mobile device to increase transmit power (POWER-UP,
also referred to as logical 0, or arithmetic -1), or decrease
transmit power (POWER-DOWN, also referred to as logical 1, or
arithmetic +1). There is a need for a method of establishing by the
mobile station whether and if so, how, to modify the transmit
diversity parameter based on feedback parameters.
[0078] Illustration 1
[0079] In the resulting sequence of TPC signals, if all the TPC
signals indicated an improvement in received signal quality, e.g.,
a 11 sequence of two TPC signals, or a 111 sequence of three TPC
signals, etc., then the set point .phi..sub.0 may be modified in
the direction of .phi..sub.1 to a new initial phase difference,
.phi..sub.0'. In some implementations, for example, .phi..sub.0'
may be set to .phi..sub.0'=.phi..sub.0+(.phi..sub.1-.phi..sub.0).
In some implementations, for example, .phi..sub.3' may be set to be
incremented by a fraction, e.g., half, or one third, or a quarter,
of (.phi..sub.1-.phi..sub.0).
[0080] Similarly, in the resulting sequence of TPC signals, if all
the TPC signals indicated a degradation in received signal quality,
e.g., a 00 sequence of two TPC signals, or a 000 sequence of three
TPC signals, then the set point .phi..sub.0 may be modified in the
opposite direction of .phi..sub.1 to a new initial phase
difference, .phi..sub.0'. In some implementations, for example,
.phi..sub.3' may be set to
.phi..sub.0'=.phi..sub.0-(.phi..sub.1-.phi..sub.0). In some
implementations, for example, .phi..sub.0' may be set to be
decremented by a fraction, e.g., half, or one third, or a quarter,
of (.phi..sub.1-.phi..sub.0).
[0081] In this illustration of an implementation of the disclosure,
all non-uniform responses may be considered inconclusive. Thus, for
example, a 01 or 10 sequence of two TPC signals, or a 001, 010,
011, 100, 101, or 110 sequence of three TPC signals, may be
considered inconclusive, in which case, the mobile device may
maintain the phase difference at .phi..sub.0, until the next
perturbation.
[0082] Illustration 2
[0083] In the resulting sequence of TPC signals, if all or a
majority of the TPC signals indicated an improvement in received
signal quality, e.g., a 110 sequence of three TPC signals, then the
set point .phi..sub.0 may be modified in the direction of
.phi..sub.1 to a new initial phase difference, .phi..sub.0', as
discussed above.
[0084] Similarly, in the resulting sequence of TPC signals, if all
or the majority of the TPC signals indicated a degradation in
received signal quality, e.g., a 001 sequence of three TPC signals,
then the set point .phi..sub.0 may be modified in the opposite
direction of .phi..sub.1 to a new initial phase difference,
.phi..sub.0', as discussed above.
[0085] If the resulting sequence of TPC signals is inconclusive,
e.g., 01 or 10 in a sequence of two TPC signals, then the mobile
device may maintain the phase difference at .phi..sub.0.
[0086] In some implementations, a distinction may be made between
majorities, resulting in a strong recommendation or a weak
recommendation. Thus, for example, or 110 may be a majority
resulting in a strong recommendation to increment .phi..sub.0 in
the direction of .phi..sub.1, because the first two responses
(i.e., to phase differences (.phi..sub.1 and .phi..sub.2, but not
.phi..sub.3) resulted in a favorable POWER-DOWN. Likewise, for
example, or 001 may be a majority resulting in a strong
recommendation to modify .phi..sub.0 in the direction opposite to
.phi..sub.1, because the first two responses (i.e., to phase
differences (.phi..sub.1 and .phi..sub.2, but not .phi..sub.3)
resulted in an unfavorable POWER-UP. However, other majorities,
e.g., 010 and 101, or possibly also 011 and 110 sequences of three
TPC signals, may be considered a weak recommendation, because they
fail to show a trend, and therefore, may be considered
inconclusive.
[0087] Illustration 3
[0088] In some implementations of the disclosure, when a TPC
sequence is inconclusive (or almost conclusive), additional logic
may be applied. According to some implementations of the
disclosure, such additional logic may be a "de-weighting" process
since the earlier power control information (TPC) have been used to
decrease or increase the transmit power for the later power control
decision at the base station, and hence affect the later TPC. To
bear out this "memory" effect, de-weighting factors, e.g., a, b, c
. . . , may be used to de-weight TPC values. The de-weighted TPC
values may be summed (e.g., a.times.TPC1+b.times.TPC2+c.times.TPC3+
. . . ) to determine the direction and value of the next move of
the base phase difference .phi..sub.0. For example, the arithmetic
values of the TPC may be used, and a, b, c . . . can be positive or
negative integers or fractional numbers.
[0089] Illustration 4
[0090] In some implementations of the disclosure, different
majorities may be associated with different modifications to
.phi..sub.0. For example, in the case of a strong recommendation,
.phi..sub.0 may be modified by (.phi..sub.1-.phi..sub.0), while in
the case of a weak recommendation, .phi..sub.0 may be modified by a
fraction of (.phi..sub.1-.phi..sub.0). For example, the fraction
may be half, quarter, or any suitable fraction of
(.phi..sub.1-.phi..sub.0).
[0091] In some implementations of the disclosure, the strength of a
majority may correspond to the amount of change in .phi..sub.0.
Thus, for example, a weak recommendation of two POWER-DOWN signals
out of a TPC sequence of three signals may result in modifying
.phi..sub.0 by a small increment in the direction of .phi..sub.1,
e.g., .phi..sub.0'=.phi..sub.0+(.phi..sub.1-.phi..sub.0)/2, while a
strong recommendation of 111 out of a TPC sequence of three signals
may result in modifying .phi..sub.0 by a larger increment in the
direction of .phi..sub.1, e.g.,
.phi..sub.0'=.phi..sub.0+(.phi..sub.1-.phi..sub.0). Likewise, for
example, a weak recommendation of two POWER-UP signals out of a TPC
sequence of three signals may result in modifying .phi..sub.0 by a
small increment in the opposite direction of .phi..sub.1, e.g.,
.phi..sub.0'=.phi..sub.0-(.phi..sub.1-.phi..sub.0)/2, while a
strong recommendation of 000 out of a TPC sequence of three signals
may result in modifying .phi..sub.0 by a larger increment in the
opposite direction of .phi..sub.1, e.g.,
.phi..sub.0'=.phi..sub.0-(.phi..sub.1-.phi..sub.0).
[0092] In some implementations, there may be different fractional
increments associated with different majorities. For example, a
weak indication of favorable change of 100 (i.e., POWER-DOWN for
.phi..sub.1, but POWER-UP for .phi..sub.2 and .phi..sub.3) may
recommend a small increment; a medium indication of favorable
change of 110 (i.e., POWER-DOWN for .phi..sub.1 and .phi..sub.2,
but POWER-UP for .phi..sub.3) may recommend a medium increment; and
a strong indication of favorable change of 111 (i.e., POWER-DOWN
for all of .phi..sub.1, .phi..sub.2 and .phi..sub.3) may recommend
a large increment. The same holds true for indications of
unfavorable change, and modifications of the nominal value in the
opposite direction. Any small, medium, and large increments may be
used, e.g., 1/4, 1/2, and 1/4 of (.phi..sub.1-.phi..sub.0),
etc.
[0093] While certain features of the disclosure have been
illustrated and described herein, many modifications,
substitutions' changes, and equivalents will now occur to those of
ordinary skill in the art. It is, therefore, to be understood that
the appended claims are intended to cover all such modifications
and changes as fall within the true spirit of the disclosure.
[0094] The examples described, and hence the scope of the claims
below, may encompass examples in hardware, software, firmware, or a
combination thereof. It will also be appreciated that the
processes, in the form of instructions having a sequence, syntax,
and content, of the present disclosure may be stored on (or
equivalently, in) any of a wide variety of tangible
computer-readable media such as magnetic media, optical media,
magneto-optical media, electronic media (e.g., solid state ROM or
RAM), etc., the form of which media not limiting the scope of the
present disclosure.
[0095] The thresholds and other attributes of the examples provided
above are not absolutes, but rather merely examples that illustrate
one or more of a variety of possibilities. Accordingly, no
limitation in the description of the present disclosure or its
claims can or should be read as absolute. The limitations of the
claims are intended to define the boundaries of the present
disclosure, up to and including those limitations. To further
highlight this, the term "substantially" may occasionally be used
herein in association with a claim limitation (although
consideration for variations and imperfections is not restricted to
only those limitations used with that term). While as difficult to
precisely define as the limitations of the present disclosure
themselves, we intend that this term be interpreted as "to a large
extent", "as nearly as practicable", "within technical
limitations", and the like.
[0096] While examples and variations have been presented in the
foregoing description, it should be understood that a vast number
of variations exist, and these examples are merely representative,
and are not intended to limit the scope, applicability or
configuration of the disclosure in any way. Various of the
above-disclosed and other features and functions, or alternative
thereof, may be desirably combined into many other different
systems or applications. Various presently unforeseen or
unanticipated alternatives, modifications variations, or
improvements therein or thereon may be subsequently made by those
skilled in the art which are also intended to be encompassed by the
claims, below.
[0097] Therefore, the foregoing description provides those of
ordinary skill in the art with a convenient guide for
implementation of the disclosure, and contemplates that various
changes in the functions and arrangements of the described examples
may be made without departing from the spirit and scope of the
disclosure defined by the claims thereto.
* * * * *